Went down to White Lion Meadow car park last night and saw, to my dismay, a family of five rats, all using the same runs and platforms that the voles had made. As I've said before, rats will eat young water voles, and drive adults out of their burrows - it happened here last year, around May/June. Luckily I'd already been in touch with NSDC, and their sympathetic pest control officer is now on the case.
Just checked now (midday) and seen a young rat, but also this vole, which I initially identified by its bottom. There's no mistaking that conker-brown fur (rats are greyer) and that hairy tail (rats' are naked and scaly).